Diminished ability to drive lower impedance loads and higher noise & distortion are potential downsides to bridging.
I'd go with the Halo - you get XLR connections and better fidelity parts. The only downsides are that the Halo has 30 peak amps (per channel) compared to 35 for the 5125 and the Halo is silver - don't think you can get it in black unless it is by special order.
Have you checked with AUDIO ADVISOR (www.audioadvisor.com)? They are a big Parasound dealer - they may have what you want in stock.
PS: My philosophy is to spend the bucks on the best speakers and amps for the front speakers - you can go budget on the other speakers. So, another option would be to buy a real nice 2 channel amp and then use a lesser expensive, less power amp on the balance of the speakers. By the way, I used my AVR as you are planning to do, for the surround speakers, but found even the little Parasound 2 channel 275 amp was far better than the AVR for just the surrounds. The more peak current the better and the AVR's simply don't have the peak current that a separate amp will have. I have four 2-channel Parasound amps in my 5.1 system with the subwoofers even having their own built-in amps.